It is known that conventional fillers in rubber compounds, such as carbon black or silica, can be replaced quantitatively or partially by rubber gels. By virtue of the low density of the rubber gels, the corresponding vulcanizates exhibit a lower weight. In addition, the use of polybutadiene-based rubber gels (BR gels) produces high impact resilience values both at room temperature and at 70° C. Such vulcanizates can be used for the production of low-damping rubber articles, especially low-damping tire components. The use of SBR-based rubber gels produces low impact resilience values at room temperature and high impact resilience values at 70° C. Corresponding vulcanizates are suitable for tire treads, for example, with an advantageous relation between wet slip behavior and rolling resistance.
Reference is made in this connection by way of example to U.S. Pat. No. 5,124,408, U.S. Pat. No. 5,395,891, DE-A 197 01 488.7, DE-A 197 01 487.9, DE-A 199 29 347.3, DE-A 199 39 865.8, DE-A 199 42 620.1.
The reinforcing effect of these rubber gels is not adequate for industrial use in vulcanizates, the term reinforcing effect referring here to the product S300×D, i.e. the product of the modulus at 300% elongation (S300) and elongation at break (D). The reinforcing effect of the rubber gels is improved by additions of suitable additives, e.g. of sulfur-containing organosilicon compounds (DE-A 19 929 347), of capped bismercaptans (DE-A 19 942 620) or of multifunctional isocyanates (DE-A 19 962 862). The disadvantage in the use of these additives, particularly in the use of multifunctional isocyanates, is that the improvement in the reinforcing effect S300×D is associated with a deterioration in the difference in impact resilience values at 70° C. and 23° C. (E70−E23).
Many areas of application of vulcanized rubber articles require both a high level of mechanical properties, especially for the product S300×D, and a high difference in resilience (E70−E23).
Therefore, there was a technical need to find measures allowing both a high level of mechanical values for S300×D and high differences in impact resilience values at 70° C. and 23° C. (E70−E23) in gel-filled rubber vulcanizates.